Homeostatic and Allostatic Principles for Behavioral Regulation in Desert Reptiles: A Robotic Evaluation

Abstract

The survival of living organisms is accomplished through regulatory behaviors. In the case of the specialist Namibian sand-diving lizards, those behaviors are modulated not only in response to external events in their immediate ecological context but also to satiate their internal drives. Both homeostasis and allostasis are endogenous processes responsible for maintaining the internal stability of animal physiological variables, in which allostasis serves as a controller coordinating multiple homeostatic subsystems. By performing homeostatic and allostatic regulation, the desert-adapted lizard can avoid extreme temperatures while being able to acquire limited resources. Moreover, a living organism can make behavioral adaptations to cope with chronic stressful situations presented by its unstable environment.Yet how multiple internal states are processed and calibrated during those processes has not been fully clarified due to how inconsistent "allostasis" is understood and applied in numerous researches. We concentrate allostatic control to behavioral adaptation without anticipation to highlight that homeostasis and allostasis offer complementary procedures to withstand immediate instability. This study integrates homeostatic and allostatic regulatory mechanisms based on interoceptive and exteroceptive cues into a simulated mobile robot replicating the lizard's sand-diving and foraging behaviors. To implement drive competition and conflict resolution in the animal's brain, we propose a computational model based on the interaction between the brainstem's medial Reticular Formation and the hypothalamus. Such a bio-inspired system is capable of action selection, and thus, can generate complex behaviors upon stimuli received from both the environment and the agent's internal states.Finally, we evaluate the robot's performance under capricious environmental settings. Our results support a dynamic, reconfigurable hierarchical organization of internal drives as an essential feature of sufficient regulation that ensures a healthier constitution.